Hydraulic pressure regulator

ABSTRACT

Described is a hydraulic pressure regulator with automatic self-relief. A control piston disposed in a regulator housing between an inlet pressure chamber and an outlet pressure chamber for a hydraulic medium is adapted to be doubly acted upon. The inlet pressure of the hydraulic medium to be regulated on the one hand and a resilient control pressure force on the other hand act on the control piston. The control piston has on its side towards the inlet pressure a smaller piston surface on a lower projecting piston part and a larger piston surface provided on an upper piston part. The lower piston part has a flow duct for the hydraulic medium, which opens beneath the larger piston surface into an upper annular groove of the control piston and which opens into a lower annular groove at the lower piston part laterally at a spacing relative to the smaller piston surface. Upon a reduction in the resilient control pressure force the control piston is moved into a position in which the flow duct is closed relative to the inlet pressure chamber. At the same time a pressure relief chamber for the hydraulic medium obtaining on the outlet side of the control piston is opened. With the hydraulic pressure regulator, when the medium ceases to be taken off out of the outlet pressure chamber the pressure in the outlet pressure chamber can be reduced or brought to zero.

The invention relates to a hydraulic pressure regulator comprising acontrol piston disposed in a regulator housing between an inlet pressurechamber and an outlet pressure chamber for a hydraulic medium.

Hydraulic pressure regulators are used primarily to convert fluctuatinginlet pressures into a constant outlet pressure. The areas of use inthat respect are for example the application of liquid adhesives in thepackaging industry or the application of paint or other coating agents.When the medium ceases to be taken off at the outlet pressure chamber,when therefore for example the application of glue or the application ofpaint is terminated or interrupted by the operator, the outlet pressurelast occurring fully obtains in the outlet pressure chamber. That givesrise to various disadvantages:

If for example closure of the applicator nozzle which is usuallyconnected to the outlet pressure chamber for the application of paint,glue or the like is not completely sealing, medium issues from thenozzle in an uncontrolled fashion as a result of the pressure in theoutlet pressure chamber. Furthermore there are agents which react in anundesirable manner under the influence of pressure. Thus it may happenfor example that, with many glues, undesirable hardening occurs as aresult of the pressure which obtains in the outlet pressure chamber andin the system connected thereto, to and including the injection nozzle.In the case of so-called plastisols, the situation may involve forexample a separation-out phenomenon, that is to say the previouslyhomogeneous mixture of substances is separated into individualcomponents and can no longer be used in that condition.

Another disadvantage is that, with a pressure obtaining in the outletpressure chamber and the system connected thereto, it is not possible tocarry out any maintenance operations or repairs as otherwise the outletpressure obtaining could possibly result in the medium being abruptlydischarged in an uncontrolled fashion.

The invention is based on the object of so designing a hydraulicpressure regulator of the kind set forth in the opening part of thisspecification that, when the medium ceases to be taken off from theoutlet pressure chamber, the pressure in the outlet pressure chamber canbe reduced as desired and - if desired - can be reduced to zero. In thatrespect, the invention seeks to take account of the requirements whichoccur in a practical context, whereby for example there is no need toprovide for pressure relief in the event of a short-term cessation inthe medium being taken off, as in that case the above-discussed adverseconsequences normally do not occur, but that when for example the mediumis to cease to be taken off for a longer period of time, the desiredreduction in pressure or complete elimination of pressure is or can beeffected.

There are no pressure regulators which, with a relatively constant inletpressure, permit stepless pressure regulation with automaticself-relief. The design of known hydraulic pressure regulators of thekind set forth in the opening part of this specification is highlyexpensive and complicated. For that reason the known pressure regulatorsare relatively heavily dependent on repair and expensive to manufacture.A further part of the object of the present invention is that ofproposing a hydraulic pressure regulator of the kind set forth in theopening part of this specification, which is of a simple structure andtherefore robust, inexpensive to manufacture and maintenance-friendlybut which at the same time has an advantageous regulationcharacteristic.

In accordance with the invention those objects are attained in that thecontrol piston is adapted to be doubly acted upon and the inlet pressureof the hydraulic medium to be regulated acts on the control piston onthe one side and a resilient control pressure force acts on the controlpiston on the other side and that the control piston, on its sidetowards the inlet pressure, has a smaller piston surface which isprovided on a lower projecting piston part and which is directly towardsthe inlet pressure medium and a larger piston surface which is providedon an upper piston part, and the lower piston part has a flow duct forthe hydraulic medium, which opens beneath the larger piston surface intoan upper annular groove in the control piston and which opens at thelower piston part into a lower annular groove laterally at a spacingrelative to the smaller piston surface, and that when the resilientcontrol pressure force is reduced the control piston is moved into aposition in which the flow duct is closed relative to the inlet pressurechamber and at the same time a pressure relief chamber for the hydraulicmedium obtaining on the outlet side of the control piston is opened.

The co-operation of the pressure force in the inlet pressure chamber andthe resilient control pressure force which opposes that pressure forceresults in an advantageous regulation characteristic, the configurationwhich is provided in accordance with the invention, of the controlpiston with the laterally opening flow duct, also contributing in thatrespect. The hydraulic pressure regulator according to the invention isof a relatively simple structure and therefore maintenance-friendly andinexpensive.

When the resilient control pressure force is reduced, the control pistonis moved upwardly by the action of the inlet pressure force so that thechamber disposed beneath the larger piston surface is increased in size.As that chamber is in direct communication with the outlet pressurechamber, that means that the volume on the outlet side is increased andthereby the outlet pressure is decreased or reduced to zero. By varyingthe magnitude of the resilient control pressure force therefore it ispossible to determine the pressure in the outlet pressure chamber andreduce it to a value of zero. Adjustment of the resilient controlpressure force can be effected for example manually by actuation of aspindle with a compression spring or for example by way of a diaphragmcylinder.

An accurate regulation characteristic on the part of the hydraulicpressure regulator is achieved by the control piston being moved in thelongitudinal direction in dependence on the inlet pressure force in theinlet pressure chamber or the resilient control pressure forcerespectively predominating. A through flow of the medium is possibleonly insofar as the lower annular groove in the control piston is openedand the medium can flow through the flow duct by way of the upperannular groove into the outlet pressure chamber. If the inlet pressurechamber predominates over the resilient control pressure force, thecontrol piston is correspondingly moved upwardly until the annulargroove has left the inlet pressure chamber and therefore no furthermedium can flow through.

In a further configuration according to the invention, it can beprovided that, for opening of the pressure relief chamber, the laterallyopening lower end of the flow duct in the lower piston part is broughtinto communication with a pressure relief duct. That is effected upon acorresponding reduction in the resilient control pressure force. Themedium which issues from the outlet pressure chamber until the pressureis completely reduced can be returned by way of the pressure relief ductin a suitable fashion. It is desirable if accumulating vessels such asfor example elastic hoses etc are arranged at the outlet side in anadjoining system.

It can also be provided that for the control piston there is an abutmentfor holding same in the position in which the flow duct is communicatedwith the pressure relief duct. By virtue of such an abutment which canalso be adapted to be adjustable or displaceable, it is possible tooperate with two adjustable outlet pressures, with an unaltered inletpressure.

In a further configuration of the invention, it can be provided that thelower piston part, in its region between the smaller piston surface andthe lower annular groove, is of a smaller diameter than in its remainingregion, so that it is possible to provide for circulation of the inletmedium by way of the pressure relief duct. That is appropriate forexample when the hydraulic medium is glues which in a stoppage conditionharden or separate out (referred to as a yoghurt effect).

The invention is described in greater detail hereinafter by means of theembodiment illustrated in the accompanying drawings in which:

FIG. 1 is a diagrammatic view in longitudinal section through anembodiment of a hydraulic pressure regulator according to the invention,and

FIG. 2 is a view corresponding to FIG. 1 but in which the control pistonis in the operative position or regulating position.

The hydraulic pressure regulator shown in the drawings has a housing 1.Provided in the housing 1 is an inlet pressure chamber 2 with adiagrammatically illustrated connection screwthread 3 for the connectionfor example of a hose screw coupling for the feed of a hydraulic mediumfrom for example a piston pump (not shown). A termination region for thescrewthread 3 is identified by reference numeral 4. Connected to theinlet pressure chamber 2 is a guide bore 5 which is provided in thehousing 1 for a lower piston part 6 of a control piston which isgenerally identified by reference numeral 7. Besides the lower pistonpart 6, the control piston 7 has an upper piston part 8 which is guidedslidably in a cylindrical recess 9 in the housing 1. The upper pistonpart 8 of the control piston 7 has piston seals 10 and 11 which arearranged in corresponding recesses in the upper piston part 8. The lowerpiston part 6 is screwed to the upper piston part 8 by way of ascrewthread 12. A screwthreaded bore 13 only serves to be able to removethe control piston for example upon dismantling from the housing 1. Thehousing 1 has an upper recess 15 which is provided with a screwthread 14and into which can be screwed a `resilient control pressure force` (notshown). That may be for example a diaphragm cylinder or the like. Inthat way, a resilient control pressure force can be applied in thedirection indicated by the arrow A to the end, which is the upper end inthe drawing, of the upper piston part 8 of the control piston 7. Aturned-out recess disposed beneath the screwthread 14 is identified byreference numeral 16. The housing 1 also has an outlet pressure chamber18 provided with an internal screwthread 17. The termination region ofthe screwthread 17 is identified by reference numeral 19. The outletpressure chamber 18 communicates by a conical region 20 with acommunicating bore 21, by means of which a communication is made betweenthe outlet pressure chamber 18 and the chamber 22 beneath the upperpiston part 8. The entire outlet pressure chamber is therefore formed bythe actual outlet pressure chamber 18, the communicating bore 21 and thechamber 22.

In its interior the lower piston part 6 of the control piston 7 has athrough-flow duct 23. The through-flow duct 23 communicates by way oftransverse bores 24 and 25 respectively with an upper annular groove 26and a lower annular groove 27 respectively in the piston part 6.

The lower piston part 6 has a piston surface 28 which is towards theinlet pressure chamber 2 and the upper piston part 8 has a pistonsurface 29 which is towards the hydraulic pressure medium. In theillustrated embodiment, the piston surface 28 is a circular pistonsurface and the piston surface 29 is an annular piston surface. Thepiston surface 28 is smaller than the piston surface 29.

As can be seen, the flow duct 23 opens beneath the larger piston surface29. The lower annular groove 27 into which the flow duct 23 also opensis arranged at a spacing relative to the smaller piston surface 28.

In addition, provided in the housing 1 is a pressure relief duct whichis identified by reference numeral 30 and which opens into an annulargroove 31 in the housing. At the opposite end the pressure relief duct30 opens into a connecting bore 32 with a screwthread 33.

An abutment for limiting the displacement travel of the control piston7, which is possible upwardly in the view shown in the drawing, isformed for by an abutment being screwed into the screwthread 14. Thatmay also be the element with which the resilient control force isapplied.

The view shown in FIG. 2 differs from that shown in FIG. 1 only in thatthe control piston 7 is moved downwardly relative to the view shown inFIG. 1. For that reason the control piston in FIG. 2 is identified byreference numeral 7' in that Figure.

The mode of operation of the hydraulic pressure regulator is as follows:

A hydraulic medium which is under pressure is fed to the inlet pressurechamber 2. The pressure is generated for example by a piston pump and istherefore subject to pressure fluctuations at the switch-over point. Thefunction of the hydraulic pressure regulator is inter alia to ensurethat the fluctuations in pressure are compensated for, in the outletpressure chamber 18. Connected to the outlet pressure chamber 18 is asystem (not shown) which ends for example in an applicator nozzle for amedium to be applied.

The inlet pressure force of the hydraulic medium acts on the controlpiston 7 from below, in the view shown in the drawing, while theresilient control pressure force acts `from above` in the directionindicated by the arrow A. In the position of the control piston 7 shownin FIG. 1, the control piston has been displaced upwardly into its upperlimit position by the action of the inlet pressure force. In thatposition there is a communication between the outlet pressure chamber18, the communicating bore 21 and the chamber 22 by way of the groove26, the transverse bores 24, the flow duct 23, the transverse bores 25,the annular groove 27 and the annular groove 31, with the pressurerelief duct 30. In that position the outlet pressure chamber 18 isrelieved of pressure. A through flow of the hydraulic medium obtainingin the inlet pressure chamber 2 is not possible.

That is a position in which maintenance operations can be carried out,nozzles can be changed or the like, in the system connected to theoutlet pressure chamber. If the nozzle outlet opening should be leaking,no medium escapes. If the lower piston part 6, in its region between thesmaller piston surface 28 and the lower annular groove 27, is of asmaller diameter than in the rest of its region (not shown), thencirculation of the hydraulic medium can take place in that position,insofar as hydraulic medium from the inlet pressure chamber 2 can passthrough the annular gap which is thus present into the annular groove 27or 31 and from there can issue through the pressure relief duct 30 andthe connection 32 and can circulate. The magnitude of the controlpressure force which acts in the direction indicated by the arrow A inthat condition is zero.

If the control piston assumes the position 7' shown in FIG. 2, thatoccurs due to the action of the resilient control pressure force actingin the direction indicated by the arrow A on the upper end of thecontrol piston. In order to reach the position 7' of the control piston,that force must be greater than the inlet pressure force acting on thesmaller piston surface 28, in the inlet pressure chamber. When theposition 7' is reached, hydraulic medium flows out of the inlet pressurechamber 2 by way of the annular groove 27, the transverse bores 25, theflow duct 23, the transverse bores 24 and the annular groove 26 into thechamber, identified by reference numeral 22' in FIG. 2, beneath thelarger piston surface 29. From there the medium can pass by way of thecommunicating bore 21 into the outlet pressure chamber 18. It is assumedthat the pressure of the inlet medium in the inlet pressure chamber 2 isalways greater than the resilient control pressure force. When thecontrol piston is in the position 7', the pressure of the inlet mediumacts not only on the smaller piston surface 28 but also on the largerpiston surface 29 so that the effective piston surface area provided inthat position is greater than in position 7. That provides on the onehand that a pressure can build up in the outlet pressure chamber 18,more specifically in accordance with the set magnitude of the resilientcontrol pressure force. On the other hand, that provides that thecontrol piston is moved upwardly, more specifically to such an extentthat the flow of the medium through the annular groove 27 is blocked. Inthat position pressure obtains both in the inlet pressure chamber 2 andalso in the outlet pressure chamber 18. If hydraulic medium is taken offfrom the outlet pressure chamber 18, the pressure in the outlet pressurechamber falls. As a result the pressure acting `upwardly` on the largerpiston surface 29 decreases. As, in that position, the pressure force inthe inlet pressure chamber, is only still acting on the smaller pistonpart 28, the resilient control pressure force in the direction indicatedby the arrow A then predominates, which means that the control piston ismoved downwardly and the annular groove 27 is partially or entirelyopened. That again permits a through-flow of medium and theabove-described procedure is continuously repeated. Pressure regulationtherefore takes place by virtue of a continuous upward and downwardmovement of the control piston.

Thus, upon a reduction in the resilient control pressure force, thepressure in the outlet pressure chamber is reduced. If the resilientcontrol pressure force is entirely removed, the control piston 7 movesinto the position which is shown in FIG. 1 and in which a pressurerelief chamber for the hydraulic medium obtaining on the outlet side ofthe control piston is opened. Either the chamber 22 or the chamber 22and in addition thereto the pressure relief duct 30 can be considered asthe pressure relief chamber.

I claim:
 1. A hydraulic pressure regulator comprising a control pistondisposed in a regulator housing comprising a control piston disposed ina regulator housing between an inlet pressure chamber and an outletpressure chamber for a hydraulic medium, characterised in that thecontrol piston (7) is adapted to be doubly acted upon and the inletpressure of the hydraulic medium to be regulated acts on the controlpiston (7) on the one hand and a resilient control pressure force (A)acts on the control piston (7) on the other hand, and that the controlpiston (7), on its side towards the inlet pressure, has a smaller pistonsurface (28) which is proved on a lower projecting piston part (6) andwhich is directly towards the inlet pressure medium and a larger pistonsurface (20) which is provided on an upper piston part (8), and thelower piston part (6) has a flow duct (23) for the hydraulic medium,which opens beneath the larger piston surface (29) into an upper annulargroove (26) in the control piston and which opens into a lower annulargroove (27) at the lower piston part (6) laterally at a spacing relativeto the smaller piston surface (28), and that upon a reduction in theresilient control pressure force (A) the control piston (7) is movedinto a position in which the flow duct (23) is closed off relative tothe inlet pressure chamber (2) and at the same time fluid pressure ofthe hydraulic medium obtaining in a relief chamber 22 on the outlet sideof the control piston (7) adjacent the large piston surface (29) isreleased.
 2. A hydraulic pressure regulator according to claim 1characterised in that the opening of the pressure relief chamber thelaterally opening lower end of the flow duct (23) in the lower pistonpart (6) is brought into communication with a pressure relief duct (30).3. A hydraulic pressure regulator according to claim 1 characterised inthat provided for the control piston (7) is an abutment for holding itin the position in which the flow duct (23) is communicated with thepressure relief duct (30).
 4. A hydraulic pressure regulator accordingto claim 1 characterised in that when the resilient control pressureforce (A) is removed the control piston (7) is moved by the pressure ofthe hydraulic medium, which acts on the smaller piston surface (28), insuch a way that the chamber (22) beneath the larger piston surface (29)is enlarged so that said chamber can act as a pressure relief chamber.5. A hydraulic pressure regulator according to claim 2 characterised inthat the lower piston part (6), in its region between the smaller pistonsurface (28) and the lower annular groove (27), is of a smaller diameterthan in its remaining region, so that circulation of the hydraulicmedium in the inlet pressure chamber (2) is possible by way of thepressure relief duct (30).